[PATCH 06/11] bsp/leon3: Improve printk() support

[Sebastian Huber]

Use the idle stack to buffer early uses of printk().  Print the buffered
characters during initialization when the UART is available and before
the idle stack is used normally.

This fix relates to a Coverity issue (PW.SET_BUT_NOT_USED).
---
 bsps/sparc/leon3/console/printk_support.c | 92 +++++++++++++----------
 1 file changed, 52 insertions(+), 40 deletions(-)

diff --git a/bsps/sparc/leon3/console/printk_support.c b/bsps/sparc/leon3/console/printk_support.c
index 2d46efce8d..760ddd4b4c 100644
--- a/bsps/sparc/leon3/console/printk_support.c
+++ b/bsps/sparc/leon3/console/printk_support.c
@@ -19,18 +19,44 @@
 #include <leon.h>
 #include <rtems/bspIo.h>
 #include <rtems/sysinit.h>
+#include <rtems/score/thread.h>
 #include <grlib/apbuart.h>
 
 int leon3_debug_uart_index __attribute__((weak)) = 0;
 struct apbuart_regs *leon3_debug_uart = NULL;
 
-/* Before UART driver has registered (or when no UART is available), calls to
- * printk that gets to bsp_out_char() will be filling data into the
- * pre_printk_dbgbuf[] buffer, hopefully the buffer can help debugging the
- * early BSP boot.. At least the last printk() will be caught.
+/*
+ * Before UART driver is available, use the idle stack to buffer early uses of
+ * printk().
  */
-static char pre_printk_dbgbuf[32] = {0};
-static int pre_printk_pos = 0;
+static size_t bsp_debug_uart_pre_init_buf_index;
+
+static void bsp_debug_uart_pre_init_out(char c)
+{
+  size_t i;
+
+  i = bsp_debug_uart_pre_init_buf_index;
+
+  if (i < _Thread_Idle_stack_size) {
+    bsp_debug_uart_pre_init_buf_index = i + 1;
+    _Thread_Idle_stacks[i] = c;
+  }
+}
+
+static void bsp_debug_uart_discard(char c)
+{
+  (void) c;
+}
+
+static void bsp_debug_uart_output_char(char c)
+{
+  apbuart_outbyte_polled(leon3_debug_uart, c, 1, 1);
+}
+
+static int bsp_debug_uart_poll_char(void)
+{
+  return apbuart_inbyte_nonblocking(leon3_debug_uart);
+}
 
 /* Initialize the BSP system debug console layer. It will scan AMBA Plu&Play
  * for a debug APBUART and enable RX/TX for that UART.
@@ -62,14 +88,29 @@ static void bsp_debug_uart_init(void)
   adev = (void *)ambapp_for_each(&ambapp_plb, (OPTIONS_ALL|OPTIONS_APB_SLVS),
                                  VENDOR_GAISLER, GAISLER_APBUART,
                                  ambapp_find_by_idx, (void *)&i);
-  if (adev) {
-    /* Found a matching debug console, initialize debug uart if present
-     * for printk
+  if (adev != NULL) {
+    size_t i;
+    size_t n;
+
+    /*
+     * Found a matching debug console, initialize debug UART if present for
+     * printk().
      */
     apb = (struct ambapp_apb_info *)adev->devinfo;
     leon3_debug_uart = (struct apbuart_regs *)apb->start;
     leon3_debug_uart->ctrl |= APBUART_CTRL_RE | APBUART_CTRL_TE;
     leon3_debug_uart->status = 0;
+
+    BSP_poll_char = bsp_debug_uart_poll_char;
+    BSP_output_char = bsp_debug_uart_output_char;
+
+    n = bsp_debug_uart_pre_init_buf_index;
+
+    for (i = 0; i < n; ++i) {
+      rtems_putc(_Thread_Idle_stacks[i]);
+    }
+  } else {
+    BSP_output_char = bsp_debug_uart_discard;
   }
 }
 
@@ -79,35 +120,6 @@ RTEMS_SYSINIT_ITEM(
   RTEMS_SYSINIT_ORDER_FOURTH
 );
 
-/* putchar/getchar for printk */
-static void bsp_out_char(char c)
-{
-  if (leon3_debug_uart == NULL) {
-    /* Local debug buffer when UART driver has not registered */
-    pre_printk_dbgbuf[pre_printk_pos++] = c;
-    pre_printk_pos = pre_printk_pos & (sizeof(pre_printk_dbgbuf)-1);
-    return;
-  }
-
-  apbuart_outbyte_polled(leon3_debug_uart, c, 1, 1);
-}
-
-/*
- *  To support printk
- */
-
-BSP_output_char_function_type BSP_output_char = bsp_out_char;
-
-static int bsp_in_char(void)
-{
-  int tmp;
-
-  if (leon3_debug_uart == NULL)
-    return -1;
-
-  while ((tmp = apbuart_inbyte_nonblocking(leon3_debug_uart)) < 0)
-    ;
-  return tmp;
-}
+BSP_output_char_function_type BSP_output_char = bsp_debug_uart_pre_init_out;
 
-BSP_polling_getchar_function_type BSP_poll_char = bsp_in_char;
+BSP_polling_getchar_function_type BSP_poll_char;
-- 
2.26.2